1. Field of the Invention
The present invention relates generally to acrylic resin compositions, and more particularly, but not by way of limitation, to acrylic-based polymeric compositions filled with particulate material and having a granite-like appearance.
2. Brief Description of the Prior Art
Polished slabs of natural granite have heretofore been used as construction materials because of the decorative appearance and durability of natural granite. However, natural granite is dense and thus, very heavy. Further, natural granite is not only brittle, but is also very expensive.
The prior art is replete with filled polymeric compositions purported to be useful as a replacement for natural granite in construction applications, such as wains coating, floor tiles, bathroom vanity tops, kitchen countertops, window sills, and the like. For example, Buser et al., U.S. Pat. No. 4,159,301 discloses a simulated granite which comprises:
(A) from about 35 to 95% by volume of a matrix consisting essentially of at least 34% by volume of a polymer, preferably an acrylic polymer, having a refractive index between 1.4 and 1.65, and about 1 to 50% by volume of at least 1 microscopic filler having an amorphous or mean crystalline axial refractive index between 1.4 and 1.65;
(B) about 0.1 to 50% by volume of macroscopic opaque particles having a optical density to visible light greater than 2.0; and
(C) about 0.1 to 50% by volume of macroscopic translucent and/or transparent particles having an optical density to visible light less than 2.0.
The ratio of the constituents (A) to (B) to (C) employed in the formulation of the simulated granite of Buser et al. is such that the optical density to visible light of a 0.05 inch thick wafer of the composite is less than 3.0. The simulated granite is prepared by making a castable composition from the ingredients (A), (B), and (C), wherein the castable composition has a kinematic viscosity no greater than 1000 stokes and a particle settling rate slow enough that it can be controllably cast onto a smooth surface and poured into a mold and cured giving a flat or shaped article having a reproducible simulated granite pattern.
Gavin, et. al., U.S. Pat. No. 4,413,089 discloses an alumina trihydrate filled polymeric composition having a substantially uniform color and desired properties of machine ability, translucency and visual depth. The alumina trihydrate filled polymeric composition is prepared by curing a glamourizable acrylic composition containing alumina trihydrate filler and a dispersion of iron oxide pigments. The iron oxide pigments are selected according to particle size to avoid interference with the desired properties of the glamourizable acrylic composition containing the alumina trihydrate filler.
While particulate filled polymeric compositions have heretofore been developed which have improved aesthetic appearances, problems have nevertheless been encountered in the use of such prior art compositions in that the cured polymeric compositions are brittle and thus easily chipped, or the polymeric compositions and articles produced therefrom are expensive to manufacture. Thus, the need has remained for improved acrylic-based polymeric compositions filled with particulate materials which have an aesthetically pleasing appearance, such as that of natural granite. Further, such improved acrylic-based particulate filled compositions should desirably be economical to manufacture, and durable so that articles poured or molded from such polymeric compositions do not easily chip without sacrificing the desired properties of weatherability, machinability, visual depth and the like. It is to such a composition that this present invention is directed.